No start suggestions (not typical) RESOLVED!

[ForcedFirebird]

May have found the issue. The fusible link has a ground to short :(

EDIT: but so does my car.

This is perplexing.

[ForcedFirebird]

Could a weak ground cause the 5v to become the ground from something else?

Getting battery drain too. Stupid gremlins...

[ForcedFirebird]

This is weird. We have continuity to ground from the ECU B+ pin until the radio fuse is pulled.

All fuses and relays were pulled, now it has 12v at the TPS with key off?

[Cabriolet]

do you have a short between the accessory power and the ignition?

[ForcedFirebird]

Not that I can see.

Started looking under the dash and a few wires were unplugged from c302. Hopefully we are getting closer to the issue.

Talked the the car owner and apparently he had someone that was going to do the 2.7i swap and told him the fuse box also needed to be swapped and had started pulling it out until I told the owner it didn't need to be. Still have a feeling something is unplugged or shorted in that area.

[ForcedFirebird]

Traced the B+ (key off) to a intermittent sticky main relay, now have 0v with key off - but only when the diagnostic cap is off, so looks like something is going on there.

Just don't get it, the engine harness has no issues when put in another car.

[LJ851]

Traced the B+ (key off) to a intermittent sticky main relay, now have 0v with key off - but only when the diagnostic cap is off, so looks like something is going on there.

Just don't get it, the engine harness has no issues when put in another car.

I know wiring can be very frustrating and bouncing ideas off other people helps me think clearer sometimes. I just want to repeat your last statement " the harness has no issues when put in another car" That means that what ever is causing this car car to act up is outside the harness or at a connection to a sub harness.

[ForcedFirebird]

Right. I am suspecting the body harness, and as mentioned before, this car was molested in the fuse box area for no reason other than the guy who was going to do the swap was an id10t.

[ForcedFirebird]

Well let's move on here.

Ok, so I decided to just put the car back together so we could move it to pull the race car out and tune it.

The race car has always had a 153 in it, plug in a 173 and OMG! SAME EXACT ISSUE! Drop in a spare 153 in the race car with an emulator hooked up and all is well. Put a 153 in this car and what do you know? IT WORKS PERFECT!

Started going over block diagrams and noticed there is one ground difference between the early and late Motronic. Pin #19 on the 173 goes to g103 on the shock tower, the 153 system has the cylinder selector and CPS spliced to #19, then going to ground (unmarked on the diagrams). It SHOULD work since they are both grounded, only difference is the location.

Sooooo, 153/173 is not as compatible as everyone thinks. Going to do more testing today, but am just happy I can tune this 153 for the customer and release the car, but would still like to know why my car with 173 harness ran the 153 for a while, no issues, then swapped in a 173 with no issues, yet when we have a 153 harness we get 12v at the two TPS leads.

[LJ851]

Excellent

[fporro]

an on this note, I too noticed wiring differences, my 87 325ic came with a 153, upgraded to 173 and am too finding differences in ms/2 # 173 grounds, etc.